mtDNA mutation inheritance

[mn382]

How did the mtDNA haplogroups arise?

I understand vey well how did Y-DNA ones appear: you have one sperm cell, with one Y chromosome, with one mutation, and this mutation will be in all the cells of the new individual, and he will inherit it to all his offspring. Over the centuries many different mutations in many different lineages result in many different Y chromosome varieties.

However this is not so simple with mtDNA, because an egg cell does not have just one mitochondrion (how many by the way?) but many, and if one mitochondrion replicates and one mutation arises in the process, its DNA still will be a small percentage of the total mtDNA of the cell, and of the total mtDNA of the new individual. So, it seems to me that it would be hard to detect these individual mutations, or that if present, they might just be a percentage in the total mtDNA of the person, and maybe during meiosis different egg cells might end up with different percentages of the mutated DNA.

So, how can they use mtDNA to trace maternal lineages just as they use Y-DNA for the paternal ones? How come different families can de differentiated according to their mtDNA differences? (sorry for using so many variants of the same word in one sentence )

Thanks in advance for your comments.

[dttom]

Actually I am not sure. But if provided when enough time, difference between mitochondria within a cell could be resolved. Say, if, one cell has 10 mts, one of which is the mutant, so in the first round of division, one of the daughter cell got the mutant. In that daughter cell, the number of 10 should be recovered when the time for second round division came, so there is a chance for two to be distributed to one of its daughter cell. The same 'enrichment' process could undergo by chance, so as to form a mutant cell with the mutant mt fixed. Just like neutral drift.